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Title: Dynamics of confined reactive water in Smectic clay-zeolite composites.

Abstract

The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the claymore » surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.« less

Authors:
 [1]
  1. IBM Watson Research Center, Yorktown Heights, NY
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1045878
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 134; Journal Issue: 6; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ACTIVATION ENERGY; ANNEALING; ATOMIC MODELS; CALCIUM; CHEMISTRY; CLAYS; CONTAINMENT; DESALINATION; DIFFUSION; HYDRATES; HYDRATION; NEUTRONS; RADIOACTIVE WASTES; RESOURCE MANAGEMENT; SCATTERING; SMECTITE; SWELLING; TEMPERATURE DEPENDENCE; WATER; ZEOLITES

Citation Formats

Pitman, Michael C., and Van Duin, Adri C. T. Dynamics of confined reactive water in Smectic clay-zeolite composites.. United States: N. p., 2012. Web. doi:10.1021/ja208894m.
Pitman, Michael C., & Van Duin, Adri C. T. Dynamics of confined reactive water in Smectic clay-zeolite composites.. United States. doi:10.1021/ja208894m.
Pitman, Michael C., and Van Duin, Adri C. T. Sun . "Dynamics of confined reactive water in Smectic clay-zeolite composites.". United States. doi:10.1021/ja208894m.
@article{osti_1045878,
title = {Dynamics of confined reactive water in Smectic clay-zeolite composites.},
author = {Pitman, Michael C. and Van Duin, Adri C. T.},
abstractNote = {The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.},
doi = {10.1021/ja208894m},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 6,
volume = 134,
place = {United States},
year = {2012},
month = {1}
}